Just thought i'd come back and update this since we actually put the baby, my niece, in the car seat today (Safety 1st Guide 65 Sport). It was a Christmas present and we opened it early. The harness, in the bottom slots, was slightly below her shoulders so she fits in it fine at 2 months old going on 3 months.

__________________Becca 25 wife to Ron 30 since 7/7/2009, momma to intact DS X born 1/15/2014
Soon to be TTC #2